Thanks Homer!
We have not cleaned it, or only a little rinse to get rid of the grit and grime before we opened her up. It was the inside that stunned me. We bought this car for $3000 with 64,000 miles about a year ago. No history really, and I have never seen an engine that clean inside!

Ok, here is the real update!
I think we have the misfire figured out....
Today after my son got home he said it was running worse than ever.
I pulled the plugs just to see if they were looking black or something. They all looked light grey as they should. I reinstalled them and it was then I did something from an old past memory. I grabbed a pair of insulated pliers and pulled the plug leads off one at a time, just to see if I could isolate the misfire to one cylinder or another.
It was very noticable that when #1 was pulled there was NO clicking as the plug boot was pulled up!
I stopped the engine and grabbed an old plug, inserted it in the lead and held it against the head. The spark was weak and inconsistant.
I pulled lead #1 out and grabbed my multimeter. Guess what.... it read OL or open... no connection!
I swapped it for an old Jeep one I had in the garage.... BINGO!
No misfire!
I dont believe it!
The leads are BERU and according to the receipt from the PO they are 18 months old!
Maybe that is it, but we need to get some new leads before we are sure!

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2009 Mercedes ML320 Bluetec